He is the one responsible for the destruction of the Kingdom of Escata, though whether he is the murderer of Henri's parents is highly debatable, but most likely. He thinks little of the human race and finds them slowly creating the road to their own inevitable downfall.
During Laura's quests he is in possession of one of the Elemental Gears, the Gloves of Venus, which he has stolen from the mines near Vaftom. The outcome of when you fight him after completing the Elemental Gear quests determines the penultimate final boss for Laura's quest.
When fighting him the first time, there is a participant limit of 1; meaning that only one character can engage him at a time. This is the only fight in the entire game with such a strict participant limit. Due to Michelle's low LP, it is highly recommended that she does not engage him at all at this time, should she be in the party. Dagul's attacks are rather weak on their own, however, he loves to chain his attacks into combos, which can also cause Paralysis. Be careful if fighting him the first time, since the battle will instantly be lost if the character is hit with this ailment, due to the participant limit. Equipping Stone Masks (a helmet with the "Null Paralysis" ability) should ensure this does not happen. If the player wins this fight, they get to keep the Gloves of Venus[*verification needed], since Basil Galeos will steal all of the other Gears, save for the Blade of Escata.
If the player loses to Dagul, he will be the penultimate-final boss, otherwise it will be Basil Galeos. The participant limit is dispelled in this second bout, so you can attack him at your leisure with the whole party, but his Paralysis ailment attacks are still effective.
For all the lines of the character, go here: